1. Field of the Invention
This invention relates generally to suspension systems for vehicles, and more particularly, to a leaf suspension arrangement that is useable with independent and semi-independent suspension systems.
2. Description of the Related Art
Leaf spring systems have for many years been used for the suspension of wheeled vehicles. The central element of a leaf spring suspension system for a vehicle is termed a “semi-elliptical” spring configured as an arc-shaped length of spring steel having a rectangular cross-section. At the center of the arc is provided an arrangement for coupling to the axle of the vehicle. At the ends are provided coupler holes for attaching the spring to the vehicle body. For heavy vehicles, leaf springs are stacked on one other to form layers of springs of different lengths. Leaf springs are still used in heavy commercial vehicles and railway carriages. In the case of very heavy vehicles, leaf springs provide the advantage of spreading the load over a larger region of the vehicle's chassis. A coil spring, on the other hand, will transfer the load to a single point.
The well-known Hotchkiss drive, the name of which derives from the French automobile firm of Hotchkiss, employs a solid axle that is coupled at its ends to the centers of respective semi-elliptical leaf springs. There are a number of problems with this form of drive arrangement. First, this drive system is characterized by high unsprung mass. Additionally, the use of a solid axle results in coupled left/right wheel motion. During heavy cornering and fast acceleration, this known system suffers from vertical deflection and wind-up.
One prior art effort to address the problems associated with the Hotchkiss system employs a parallel leaf spring arrangement at each end of a solid axle. This known arrangement affords increased axle control, in the form of reduced power hop. Other advantages of this known arrangement include roll under steer, auto load leveling and the gross vehicle weight, and no frame changes are required to convert from a Hotchkiss system. However, the known parallel leaf spring arrangement employs a solid axle, and therefore does not provide the benefits of independent suspension. In addition, this known arrangement is plagued with the disadvantage of high unsprung mass.
A de Dion tube vehicle suspension arrangement is a form of semi-independent suspension and constitutes an improvement over the Hotchkiss drive. In this type of suspension, universal joints are employed at the wheel hubs and the differential, and there is additionally provided a solid tubular beam that maintains the opposing wheels in parallel. The de Dion tube is not directly connected to the chassis and is not intended to flex.
The benefits of a de Dion suspension include a reduction in the unsprung weight compared to the Hotchkiss drive. This is achieved by coupling the differential to the chassis. In addition, there are no camber changes during suspension unloading. Since the camber of both wheels is set at zero degrees, the traction from wide tires is improved, and wheel hop under high power operations is reduced compared to an independent suspension. However, the de Dion tube adds unsprung weight.
It is, therefore, an object of this invention to provide a vehicle suspension arrangement that provides the benefits of independent suspension while using leaf spring technology.
It is another object of this invention to provide a vehicle suspension arrangement that employs leaf spring technology and yet affords reduced unsprung mass for reduced inertial effects and improved vehicle handling response.
It is also an object of this invention to provide a vehicle suspension arrangement that employs leaf spring technology and affords reduced suspension inertia.
It is a further object of this invention to provide a vehicle suspension arrangement that employs leaf spring technology and affords reduced noise, vibration, and harshness (NVH).
It is additionally an object of this invention to provide a vehicle suspension arrangement that employs leaf spring technology and affords reduced lateral wheel shake.
It is yet a further object of this invention to provide a vehicle suspension arrangement that employs leaf spring technology and affords reduced side view wind-up at the axle bracket.
It is also another object of this invention to provide a vehicle suspension arrangement that employs leaf spring technology and affords reduced forward and rearward movement.
It is yet an additional object of this invention to provide a vehicle suspension arrangement that employs leaf spring technology and affords a semi-independent suspension effect during asymmetric wheel travel.
It is yet an additional object of this invention to provide a vehicle suspension arrangement that employs leaf spring technology in combination with a coil spring element.